Without limiting the scope of the present invention, its background will be described in relation to forming a window in a casing string for a multilateral well, as an example.
In multilateral wells, it is common practice to drill a branch or lateral wellbore extending laterally from an intersection with a main or parent wellbore. Typically, once the casing string is installed and the parent wellbore has been completed, a deflection assembly such as a whipstock is positioned in the casing string at the desired intersection and then one or more mills are deflected laterally off of the whipstock to form a window through the casing sidewall.
In certain installations, it is desirable to drill the lateral wellbore in a predetermined direction from the parent wellbore such as out of the high side of the parent wellbore. In such installations, it is necessary to form the window at a predetermined circumferential orientation relative to the parent casing. In order to properly position and rotationally orient the whipstock such that the window is milled in the desired direction, a latch assembly associated with the whipstock is anchored into and rotationally oriented within a latch coupling interconnected in the casing string. The latch assembly typically includes a plurality of spring operated latch keys, each of which having an anchoring and orienting profile that is received in a latch profile formed internally within the latch coupling. In this manner, when the latch keys of the latch assembly are operatively engaged with the latch profile of the latch coupling, the latch assembly and the equipment associate therewith are axially and circumferentially anchored and rotationally oriented in the desired direction within the casing string.
It has been found, however, that in certain well installations such as deep or extended reach wells, rotationally securing a latch assembly within a latch coupling may be difficult. In typically practice, once the latch assembly is substantially on depth, the tool string carrying the latch assembly is slowly rotated and lowered into the well. This operation is intended to axially positioned the latch assembly in the latch coupling and rotationally align the latch assembly in the latch coupling in the desired circumferential orientation as indicated by a torque signal at the surface. In the aforementioned deep or extended reach wells, however, delay in the torque signal reaching the surface due to torsional flexibility and wind up of the worksting, for example, may result in over stressing the latch keys, release of the latch assembly from the latch coupling or other failure.
Accordingly, a need has arisen for an improved system for circumferentially aligning a downhole latch subsystem in a subterranean well. In addition, a need has arisen for such an improved system that is operable for use in deep or extended reach wells. Further, a need has arisen for such an improved system that does not risk over stressing the latch keys or releasing the latch assembly from the latch coupling during circumferential orientation.